>Second, Apple just reduces it during "peak times" not matter what is actually used for production of electricity

The Apple support article says otherwise https://support.apple.com/en-us/HT213323

>But your charging your iPhone is not enough, even all owners, to reduce expected demand.

I'm not sure why that is reason to not make a change? Most people most of the time charging at home don't need their phone topped up extremely quickly, and if you do, there's an easy way to override it.

Are we only allowed to make improvements if they're significant?

Sure I'd hate if Apple marketed it as a massive impact, just like when they marketed their "smaller boxes" after taking out chargers. But it is objectively an improvement, even if minor. Plus if Apple, Microsoft, Google and a host of others all incorporate energy saving features, it does have an impact.